The present invention is related to a pipetting device with an upper part of the casing and a lower part of the casing, detachably connectable with the upper part of the casing, which has at least one seat for detachably holding a pipette point.
Pipetting devices are used in the laboratory, in particular, for the dosing of liquids. These are picked up and discharged in pipette points via a tip opening. In air cushion pipettes, a displacement equipment for a gas is integrated into the pipetting device and communicatingly connected with the pipette point through a hole in the seat. An air cushion is displaced by means of the displacement equipment, so that liquid is aspirated into the pipette point and ejected from it. Mostly, the displacement equipment is a cylinder with a plunger movable therein.
The pipette point is detachably held in its seat, so that it can be replaced by a new pipette point after use. Through this, carryovers and contaminations can be avoided at subsequent dosings. Pipette points for one time use are available from plastics at a reasonable price.
In air cushion pipettes, contamination of the displacement equipment, and of the lower part of the pipette casing in particular, can take place. Therefore, it is desirable to realise the pipette casing in two parts with a lower part of the casing and an upper part of the casing, which are separable from each other for the purpose of autoclaving, for instance. Further, it may be desirable to replace lower parts of the casing by displacement equipments, in order to use the pipetting device at different volume ranges. Finally, a one channel pipette can be transformed into a multi-channel pipette, or the number of channels of a multi-channel pipette can be changed.
From EP 0 428 500 B1, the entire contents of which is hereby incorporated by reference in its entirety, a pipetting device with a displacement equipment in a lower part of the casing is already known, which is screwable on the shaft of an upper part of the casing with a drive equipment for the displacement equipment via an union nut. However, the exchange of the lower part of the casing is arduous, time-consuming and troublesome. For the use of threads, the assembly is lavish. In addition, unintentional separation of the lower part of the casing from the upper part of the casing can easily occur due to the thread connection.
From GB 2 1616 398 A, the entire contents of which is hereby incorporated by reference in its entirety, a pipette with a snap connection between the lower part of the casing and the upper part of the casing is know. The lower part of the casing is connected with the upper part of the casing via a coupling, which has hook-shaped flanges which snap into the receivers of the upper part of the casing. Unlocking the parts of the snap connection from each other is difficult when the snap connection is dimensioned such that the lower part of the casing and the upper part of the casing are connected with each other with sufficient security. When the strength of the snap connection is reduced, there is a danger that the lower part of the casing and the upper part of the casing are unintentionally separated from each other when used.
Departing from this, the present invention is based on the objective to provide a pipetting device in which the upper part of the casing and the lower part of the casing can be easily separated from each other and can be connected with each other with great security in spite of this.